1. Field of the Invention
The present invention relates to a digital versatile disk (DVD), and an apparatus and method for playing the DVD, and more particularly, to an audio DVD (hereinafter referred to as xe2x80x9cDVD-Audioxe2x80x9d) and an apparatus and method for playing the same.
2. Description of the Related Art
Recently, there has been developed a so-called video DVD (hereinafter referred to as xe2x80x9cDVD-Videoxe2x80x9d), which has a considerably higher storage capacity than a laser disk (LD) so as to realize a significantly improved picture and sound quality. If the DVD is employed to store and retrieve only audio data, such DVD is called a DVD-Audio. The DVD-Audio provides means for storing and retrieving a large amount of audio data having a significantly improved quality compared to a compact disk (CD) or a digital audio tape (DAT).
The conventional CD stores an audio signal as linear pulse code modulated (PCM) audio data quantized into 16 bits by employing a sampling frequency of 44.1 KHz. The digital data stored in the CD is converted into analog signals by means of a CD player. The CD is much more convenient to use as compared to the previous microgroove phonograph record (LP), but is regarded as having a lower sound quality than the analog LP. This is because the audio signals are sampled at 44.1 KHz and quantized into 16 bits to be stored into a CD. Moreover, the audible frequency range may be over 20 KHz, and the dynamic range must be over 120 dB. In addition, the CD can only store audio signals of at most two channels, and therefore is impossible to store and reproduce the audio data concerned with multi-channel music. In these circumstances, there have been proposed various methods to improve the sound quality of the CD by increasing the numbers of the sampling frequency and the audio channels.
The DVD provides means to record video and audio data at high density. In this case, the video data is recorded in the MPEG (Moving Picture Expert Group) while the audio data is recorded in the linear PCM format, dolby AC-3 format, MPEG format, etc. Hence, the DVD-Video player is designed to reproduce both video and audio data recorded in a DVD-Video. Such a DVD-Video prepared to necessarily store video data is very uneconomical in view of the storage space when used for storing audio data only.
The audio data recorded in a DVD-Video has a much higher quality than that in a CD since the audio data of the DVD has a higher sampling frequency and larger numbers of quantization bits and channels than that of the CD. Namely, the DVD player reproduces high quality audio data in multiple channels.
The DVD is possible to transfer data at 10.08 Mbps at most. This makes it possible to reproduce data sampled at 192 KHz in two channels. This also approaches the maximum sampling frequency proposed as a prerequisite for the next advanced audio system at the Advanced Digital Audio Conference held in Japan in April, 1996. Thus, if audio data are recorded in a DVD-Audio, the DVD player may reproduce sounds of a significantly improved quality over that reproduced from the DVD-Video.
It is an object of the present invention to provide a DVD-Audio for storing digital audio signals sampled at the maximum sampling frequency and quantized in the maximum number of bits with the number of channels limited by the data transfer speed in linear PCM.
It is another object of the present invention to provide a DVD-Audio for compressively coding digital audio signals sampled at the maximum sampling frequency and quantized in the maximum number of bits and storing them with the number of channels limited by the data transfer speed and the coding system in linear PCM.
It is still another object of the present invention to provide a DVD player for playing a DVD-Audio recorded in linear PCM and a method therefor.
It is a further object of the present invention to provide a DVD player for playing a DVD-Audio recorded with audio data compressively coded and a method therefor.
It is further another object of the present invention to provide a DVD player for properly playing a DVD-Video or DVD-Audio by distinguishing them.
According to a first aspect of the present invention, a DVD-Audio includes a data zone for storing data to be reproduced and an information zone for storing information on the data, the information zone including directories of a video title set (VIDEO_TS) and an audio title set (AUDIO_TS), wherein the AUDIO_TS directory includes information on an audio manager (AMG) having information on audio titles, wherein the data zone includes the audio titles each having audio title set information (ATSI) followed by a plurality of contiguous audio objects (AOBs), the ATSI includes a plurality of audio stream attributes each having an audio coding mode indicator, first to third quantization bit numbers, first to third sampling frequencies and decoding algorithm information relating to the number of audio channels, and each of the AOBs includes a plurality of audio packs recorded with audio data corresponding to the decoding algorithm stored in the audio stream attribute.
According to a second aspect, an apparatus for playing the inventive DVD-Audio includes a data receiver for receiving the audio data retrieved from the DVD-Audio, a controller for generating an audio control signal containing an audio coding mode indicator, a sampling frequency, a channel number and quantization information by analyzing information on the audio data or stopping the playing operation according to whether the AUDIO_TS is detected to have effective data, an audio decoder to decode the received audio data and to multi-channel mix, sampling-frequency convert and requantize the decoded audio signal according to the audio control signal, and an audio output circuit to convert the decoded audio data into an analog audio signal.
According to a third aspect, a method for playing the inventive DVD-Audio includes the steps of locating the AMG when the AUDIO_TS directory includes an effective data, checking out all information of the DVD-Audio from the information of the AMG, reading the data of the position of an audio title selected according to the position information of the AMG when receiving a command for reproducing the audio title, and setting the audio decoder to carry out the algorithm for reproducing the audio title by reading the audio stream attribute of the audio title set information management table (ATSI_AMT).
The present invention will now be described more specifically with reference to the drawings attached only by way of example.